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The Result We Wanted

Fiction · 3 min read

The science fair was on Friday. It was Wednesday night, and Mira's result was wrong.

She had checked the numbers twice and found no error. They just were not the numbers she had promised. For six weeks she and her lab partner, Joss, had tested whether plants grew taller under blue light than under red. Their hypothesis, written on the poster in their best handwriting, said blue would win. Their teacher, Ms. Okafor, had already put their project forward for the regional round.

Twenty plants under each light. They had measured every one with a ruler, every other day. And the data, sitting in the spreadsheet, said that the red-light plants were, on average, 0.4 centimeters taller. A difference so small that a single bumped pot could have caused it.

"It's the wrong way round," said Joss. He had come over to her house with a bag of chips and a worried face. "If we show this, we lose. Nobody gets to regionals with a result like this."

"We could just say there was no difference."

"No difference is boring." Joss scrolled the spreadsheet. "Look, plant seventeen. It's the one under the blue lamp that got knocked on day nine. It's obviously an outlier. If we take it out, and plants four and eleven, which the cat sat on, then blue is ahead by half a centimeter."

Mira looked at the three rows. Plant seventeen had been knocked, true. Plants four and eleven, the cat had sat on, also true. That made removing them feel almost reasonable. But then she noticed that those three plants had all been in the blue group. And that two plants in the red group had been damaged too, by Joss himself, when he moved the tray, and those were not on the list of things to remove.

"If we throw out damaged plants," she said slowly, "we have to throw out all the damaged ones. Red too. Taking out only blue's casualties would be bias, even if every plant really was damaged."

"That's not what I meant."

"I know what you meant."

Joss stopped scrolling. Neither of them said anything for a while. In the next room, Mira's father was watching a football game with the sound low.

"Okay," Joss said at last. "What happens if we remove all five?"

She did it. It took twenty seconds. The difference came back as 0.1 centimeters in favor of red, which is to say nothing.

"So the honest answer is that our experiment showed no clear difference between blue and red light for this plant."

"Which is a lousy poster."

"Is it?" Mira was surprised at her own voice. "We tested something. Most people just assume blue is better because they heard it somewhere. We checked, with a fair sample of twenty plants each. Nobody else at this fair has checked it for this plant. It's small, but it's ours, and it's true."

Joss rubbed his face. "Ms. Okafor is going to be so disappointed."

"Maybe." Mira opened a new slide and typed a title: Does the color of light change how tall a plant grows? Below it, in a larger font: We found no clear difference. And below that: What we would try next.

On Friday they stood beside the poster for two hours. Most people walked past. But a judge in a gray cardigan stopped, read the whole thing, and asked one question: "Did you remove any data?"

"We considered it," said Mira. "We decided that if we removed any, we had to remove everything damaged, and then it didn't change anything. So we kept all the data and wrote down why."

The judge nodded slowly. She wrote something on her clipboard. Mira could not read it, and did not ask.

Words in this story: hypothesis, outlier, bias, sample, data